Apparatus for controlling motive power transmission in vehicle

ABSTRACT

A power transmission control apparatus for a vehicle c has a plurality of fork shafts coupled with “sleeves engageable with free-rotating gears”, including first and second fork shafts. When both the first and second fork shafts are in neutral positions, the first and second fork shafts are not coupled in the axial direction so that, while one fork shaft is maintained in its neutral position, the other fork shaft is movable by an actuator from its neutral position to its meshing position. When the one fork shaft is in its neutral position and the other fork shaft is in its meshing position, the first and second fork shafts are coupled in the axial direction so that, when the one fork shaft is moved from its neutral position to its meshing position by the actuator, the other fork shaft is simultaneously moved from its meshing position to its neutral position.

TECHNICAL FIELD

The present invention relates to an apparatus for controlling motivepower transmission in a vehicle (hereinafter referred to as a “powertransmission control apparatus for a vehicle”).

BACKGROUND ART

Conventionally, there has been a power transmission control apparatusfor a vehicle which includes a transmission having a plurality of gearstages and controls shifting among the gear stages of the transmissionthrough use of actuators (see, for example, Patent Document 1).

In the transmission of such an apparatus, a plurality of fork shafts areprovided. Each fork shaft is movable in the axial direction between itsneutral position and a meshing position, independently of the remainingfork shafts. In a state in which one fork shaft is located in itsmeshing position and all the remaining fork shafts are located in theirneutral positions, a sleeve coupled with the one fork shaft comes intoengagement with a free-rotating gear for a gear stage corresponding tothe meshing position. As a result, the free-rotating gear is unrotatablyfixed to a shaft on which the free-rotating gear is provided, wherebythe gear stage corresponding to the meshing position is realized. Theposition of each fork shaft in the axial direction is controlled by anactuator.

In this transmission, when a gear shift from the current gear stage toan adjacent gear stage (so-called “sequential shift”) is performed,first, a fork shaft corresponding to the current gear stage is moved bythe actuator to its neutral position from its meshing position for thatgear stage. Namely, there is a attained a state in which all the forkshafts are located in their neutral positions. Thus, the state of thetransmission changes from a “state in which the current gear stage hasbeen realized” to neutral (a state in which no gear stage is realized).Subsequently, a fork shaft corresponding to the adjacent gear stage ismoved by the actuator from its neutral position to is meshing positionfor that gear stage. As a result, the state of the transmission changesfrom neutral to a “state in which the adjacent gear stage has beenrealized.” As described above, in the case of sequential shift, a gearstage to be used after the shift operation (hereinafter simply referredto as the “gear stage after the shift operation”) is “realized” afterthe “cancellation” of the gear stage used before the shift operation(hereinafter simply referred to as the “gear stage before the shiftoperation”).

In addition, in this transmission, a gear shift (so-called “skip shift”)from the current gear stage to a gear stage (hereinafter, referred to asa “nonadjacent gear stage”) which is two or more gear stages apart fromthe current gear stage can be performed. In the skip shift, after thestate of the transmission has changed to neutral from the “state inwhich the current gear stage has been realized,” a fork shaftcorresponding to the nonadjacert gear stage is moved from its neutralposltion to its meshing position for that nonadjacent gear stage.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Laid-Open (kokai) No.2006-97740

SUMMARY OF THE INVENTION

In the case of a power transmission control apparatus including theabove-described transmission, a vehicle cannot be accelerated over aneutral period in the shift operation between the “operator ofcancelling the gear stage before the shift operation” and the “operationof realizing the gear stage after the shift operation.” Accordingly,there has been demand for shortening the neutral period to the extentpossible.

The present invention has been accomplished in view of theabove-described point, and its object is to provide a power transmissioncontrol apparatus for a vehicle which controls shift operation of atransmission among gear stages through use of actuators and which canshorten the neutral period in the shift operation and can perform skipshift.

The feature of the power transmission control apparatus for a vehicleaccording io the present invention resides in provision of a couplingmechanism which can couple first and second fork shafts among aplurality effort shafts in the axial direction. The coupling mechanismis configured such that when both the first and second fork shafts arelocated in their neutral positions, the coupling mechanism does notcouple the first and second fork shafts in the axial direction so that,white one of the first and second fork shafts is maintained in itsneutral position, the other of the first and second fork shafts can bemoved, through drive of the actuator, from its neutral position to thecorresponding meshing position. Further, the coupling mechanism isconfigured such that when the one fork shaft is located in its neutralposition and the other fork shaft is located in the correspondingmeshing position, the coupling mechanism couples the first and secondfork shafts in the axial direction so that, when the one fork shaft ismoved from its neutral position to the corresponding meshing positionthrough drive of the actuator, the other fork shaft is simultaneouslymoved from the corresponding meshing position to its neutral position.

Accordingly, in the case where a gear shift from “a gear stagecorresponding to the meshing position of the other fork shaft” to “agear stage corresponding to the meshing position of the one fork shaft”is performed, the operation of cancelling the gear stage before theshift operation and the operation of realizing the gear stage after theshift operation are performed simultaneously. Accordingly, the neutralperiod becomes shorter as compared with the case of a conventionalapparatus in which the “operation of realizing the gear stage after theshift operation” is performed after the “operation of cancelling thegear stage before the shift operation.”

In addition, the above-described apparatus according to the presentinvention can move each fork shaft between its neutral position and acorresponding meshing position while maintaining all the remaining forkshafts in their neutral positions. Accordingly, after the fork shaftcorresponding to the currently realized gear stage has moved to itsneutral position from the meshing position corresponding to that gearstage, any fork shaft can be moved from its neutral position to ameshing position. Namely, by performing the “operation of realizing thegear stage after the shift operation” after the “operation of cancellingthe gear stage before the shift operation” as in the case of theconventional apparatus, the “skip shift” can be performed as in the caseof the conventional apparatus. In summary, the present apparatus canshorten the neutral period in the shift operation and can perform theskip shift.

In the above-described apparatus according to the present invention,each of the fort shafts may have two heads which are separated from eachother in the axial direction and which correspond to two of a pluralityof the gear stages, and the transmission may include a shift andselection shaft which is provided to be movable in the axial directionand rotatabfe about its axis and which has an inner lever protrudingfrom a circumferential surface of the shift and selection shaft. Thisshift and selection shaft is driven by the above-mentioned actuator.

In this case, a distance obtained by subtracting, from a distancebetween the two heads provided on the fork shaft, a moving distance ofthe fork shaft from the neutral position to the meshing position, ispreferably greater than a width of the inner lever as measured in theaxial direction of the fork shaft.

By virtue of the above-described configuration, in the case where thegear shift from “the gear stage corresponding to the meshing position ofthe other fork shaft” to “the gear stage corresponding to the meshingposition of the one fork shaft” is performed, it is possible to move theinner lever from a position between the two heads provided on the otherfork shaft to a position between the two heads provided on the one forkshaft while maintaining the other fork shaft in the meshing position(namely, without performing the “operation of cancelling the gear stagebefore the shift operation”). Thereafter, by pressing either one of thetwo heads of the one fork shaft in the axial direction by the innerlever, the one fork shaft is moved from its neutral position to itsmeshing position, whereby the “operation of cancelling the fear stagebefore the shift operation” and the “operation of realizing the gearstage after the shift operation” are performed simultaneously asdescribed above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a vehicular power transmission controlapparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view showing the positional relation between anS&S shaft and a plurality of fork shafts in neutral in the transmissionshown in FIG. 1.

FIG. 3 is a pair of schematic views showing the state of engagementbetween a “sleeve and a fork shaft” and the S&S shaft in thetransmission shown in FIG. 1.

FIG. 4 is a set of schematic views showing the states of the pluralityof fork shaft in a state in which each gear stage is realized in thetransmission shown in FIG. 1.

FIG. 5 is a pair of views used for describing the relation between thedistance between a pair of heads and the width of an inner lever.

FIG. 8 is a set of views used for describing an operation for asequential shift from a second gear stage to a third gear stage in thetransmission shown in FIG. 1.

FIG. 7 is a set of views used for describing an operation for asequential shift from the second gear stage to a first gear stage in thetransmission shown in FIG. 1.

FIG. 8 is a set of views used for describing an operation for a skipshift from the third gear stage to the first gear stage in thetransmission shown in FIG. 1.

FIG. 9 is a set of views corresponding to those of FIG. 4 and relatingto a transmission according to a modification of the transmission shownin FIG. 1.

FIG. 10 is a first set of views corresponding to those of FIG. 4 andrelating to a transmission according to a second modification of thetransmission shown in FIG. 1.

FIG. 11 is a second set of views corresponding to those of FIG. 4 andrelating to a transmission according to the second modification of thetransmission shown in FIG. 1.

FIG. 12 is a view corresponding to FIG. 2 and relating to a transmissionaccording to a third modification of the transmission shown in FIG. 1.

FIG. 13 is a set of views corresponding to those of FIG. 4 and relatingto the transmission shown in FIG. 12.

FIG. 14 is a set of views corresponding to those of FIG. 6 and relatingto the transmission shown in FIG. 12.

FIG. 15 is a set of views corresponding to those of FIG. 7 and relatingto the transmission shown in FIG. 12.

FIG. 16 is a set of views corresponding to those of FIG. 8 and relatingto the transmission shown in FIG. 12.

FIG. 17 is a set of views corresponding to those of FIG. 13 and relatingto a transmission according to a modification of the transmission shownin FIG. 12.

MODE FOR CARRYING OUT THE INVENTION (Overall Configuration)

A vehicular power transmission control apparatus according to anembodiment of the present invention (hereinafter referred to as the“present apparatus”) will now be described with reference to thedrawings. As shown in FIG. 1, the present apparatus includes atransmission T/M, a friction clutch C/T, a clutch actuator ACT1, a shiftactuator ACT2, and an electronic control unit (ECU). The presentapparatus is also called an automated manual transmission (AMT).

The transmission T/M is a transmission which does not include a torqueconverter (a so-called manual transmission). The transmission T/M has aninput shaft A2 to which power is input from a drive output shaft A1 ofan engine E/G which is a well-known internal combustion engine, and anoutput shaft A3 from which power is output to drive wheels of thevehicle. The drive output shaft A1 and the input shaft A2 are disposedcoaxially with each other, and the input shaft A2 and the output shaftA3 are disposed in parallel with each another. The input shaft A2 andthe output shaft A3 are supported by a housing (not shown) of thetransmission T/M such that they cannot move in the axial direction andcan rotate about their axes. The transmission T/M has sk gear stages (afirst gear stage (1st) to a sixth gear stage (6th)) for advancing thevehicle. The state of the transmission T/M is controlled by the shiftactuator ACT2. The details of the structure of the transmission T/M willbe described later.

The friction clutch C/T is a well known flat plate clutch disposedbetween the drive output shaft A1 of the engine E/G and the inptil shaftA2 of the transmission T/M. The friction clutch C/T is configured suchthat it can selectively realize an “engaged state” in which a powertransmission system is formed between the drive output shaft A1 and theinput shaft A2 and a “disengaged state” in which the power transmissionsystem is not formed. The state of the friction clutch C/T is controlledby the clutch actuator ACT1. Therefore, the friction clutch C/T does nothave a clutch pedal operated by a driver.

The ECU controls the clutch actuator ACT1 (accordingly, the state of thefriction clutch C/T) and the shift actuator ACT2 (accordingly, the stateof the transmission T/M) on the basis of information from varioussensors, such as a sensor for detecting the amount of operation of anaccelerator pedal (accelerator opening) of the vehicle, a sensor fordetecting the position of a shift lever of the vehicle, and a sensor fordefecting the speed of the vehicle, all of which are not shown.

(Structure of the Transmission T/M)

The structure of the transmission T/M will be described specificallywith reference to FIGS. 1 to 8. As shown in FIG. 1, the transmission T/Mincludes a plurality of fixed gears (also referred to as “drive gears”)G1 i, G2 i, G3 i, G4 i, G5 i, and G6 i; and a plurality of free-rotatinggears (also referred to “driven gears”) G1 o, G2 o, G3 o, G4 o, G5 o,and G6 o. The feed gears G1 i, G2 i, G3 i, G4 i, G5 i, and G6 icorrespond to the first, second, third, fourth, fifth, and sixth gearstages for forward movement, and are unrotatably fixed to the inputshaft A2 to be coaxially with the input shaft A2 and be unmovabie in theaxial direction in relation to the input shaft A2.

The free-rotating gears G1 o, G2 o, G3 o, G4 o, G5 o, and G6 ocorrespond to the first, second, third, fourth, fourth, and sixth gearstages for forward movement, and are rotatably provided on the outputshaft A3 to be coaxial with the output shaft A3 and be unmovable in theaxial direction in relation to the output shaft A3. The free-rotatinggears G1 o, G2 o, G3 o, G4 o, G5 o, and G6 o are always in meshingengagement with the fixed gears G1 i, G2 i, G3 i, G4 i, G5 i, and G6 i,respectively.

The transmission T/M includes sleeves S1, S2, and S3. The sleeves S1,S2, and S3 are unrotatably provided on the output shaft A3 to be coaxialwith the output shaft A3 and be movable in the axial direction inrelation to the output shaft A3. The sleeve S1 is engageable with thefree-rotating gears G1 o and G4 o for the first and fourth gear stages.The sleeve S2 is engageable with the free-rotating gears G5 o and G2 ofor the fifth and second gear stages. The sleeve S3 is engageable withthe free-rotating gears G3 o and G6 o for the third and sixth gearstages.

As shown in FIGS. 2 and 3, the transmission T/M includes fork shaftsFS1, FS2, and FS3. The fork shafts FS1, FS2, and FS3 are supported bythe housing (not shown) of the transmission T/M such that they can movein the axial direction, they cannot rotate about their axes, and areparallel to one another. As show in FIG. 3, the fork shafts FS1, FS2,and FS3 are coupled with the sleeves S1, S2, and S3, respectively, suchthat each of them cannot move in the axial direction in relation to thecorresponding sleeve.

When all the fork shafts FS1, FS2, and FS3 are located in their neutralpositions in the axial direction (positions shown in FIG. 2), none ofthe sleeves S1, S2, and S3 are in engagement with the correspondingfree-rotating gears. As a result, a neutral state (a state in which apower transmission system is not formed between the input shaft A2 andthe output shaft A3) is realized.

When the fork shaft FS1 moves from the neutral position (the positionshown in FIG. 2) to the meshing position for the first gear stage (thefourth gear stage) (leftward (rightward) in FIG. 2), the sleeve S1 comesinto engagement with the free-rotating gear G1 o (G4 o), so that thefree-rotating gear G1 o (G4 o) is fixed to the output shaft A3 so as tobe unrotatable relative to the output shaft A3. As a result, the firstgear stage (the fourth gear stage) is realized. A state in which a gearstage is “realized” means a “state in which only the free-rotating gearfor that gear stage is unrotatablly fixed to the output shaft A3 and thefree-rotating gears for all the remaining gear stages are maintainedrotatable in relation to the output shaft A3.” In other words, the statein which a gear stage is “realized” refers to a “state in which a powertransmission system having a reduction ratio (the ratio of therotational speed of the input shaft A2 to the rotational speed of theoutput shaft A3) of that gear stage is formed between the input shaft A2and the output shalt A3.”

Similarly, when the fork shaft FS2 moves from the neutral position (theposition shown in FIG. 2) to the meshing position for the fifth gearstage (the second gear stage) (leftward (rightward) in FIG. 2), thesleeve S2 comes into engagement with the free-rotating gear G5 o (G2 o),whereby the fifth gear stage (the second gear stage) is realized. Whenthe fork shaft FS3 moves from the neutral position (the position shownin FIG. 2) to the meshing position for the third gear stage (the sixthgear stage) (leftward (rightward) in FIG. 2), the sleeve S3 comes intoengagement with the free-rotating gear G3 o (G6 o), whereby the thirdgear stage (the sixth gear stage) is realized.

A head H1 is fixed to the fork shaft FS1 and has a head portion for thefirst gear stage (hereinafter referred as the “1st head”) and a headportion for the fourth gear stage (hereinafter referred as the “4thhead”) which are spaced from each other in the axial direction. A headH2 is fixed to the fork shaft FS2 and has a head portion for the fifthgear stage (hereinafter referred as the “5th head”) and a head portionfor the second gear stage (hereinafter referred as the “2nd head”) whichare spaced from each other in the axial direction. A head H3 is fixed tothe fork shaft FS3 and has a head portion for the third gear stage(hereinafter referred as the “3rd head”) and a head portion for thesixth gear stage (hereinafter referred as the “6th head”) which arespaced from each other in the axial direction. The heads for therespective gear stages project radially from the circumferentialsurfaces of the corresponding fork shafts.

As shown in FIGS. 2 and 3, the transmission T/M has a shift andselection shaft (hereinafter referred to as the “S&S shaft”). The S&Sshaft is supported by the housing (not shown) of the transmission T/Msuch that if is relatively movable in the axial direction and berotafable about its axis. An inner lever IL radially projects from thecircumferential surface of the S&S shaft.

As a result of rotation of the S&S shaft about its axis, one of the forkshafts FS1, FS2, and FS3 is selected, and the inner lever IL enters thespace between the two heads provided on the selected fork shaft (seeFIGS. 2 and 3). When the S&S shaft is moved in the axial direction inthis state, the inner lever IL presses either one of the two heads ofthe selected fork shaft in the axial direction. As a result, theselected fork shaft moves in the axial direction from the neutralposition to the meshing position for the gear stage corresponding to thepressed head. As a result, the gear stage corresponding to the pressedhead is realized.

Specifically, the shift actuator ACT2 (see FIG. 1) includes a shiftmotor and a selection motor (see FIG. 3). The selection motor rotatesthe S&S shaft about its axis (selection operation). The shift motordrives the S&S shaft in the axial direction (shift operation).Accordingly, the neutral and the first through sixth gear stages can beselectively realized by controlling the selection motor and the shiftmotor (namely, performing the selection operation and the shiftoperation).

As shown in FIG. 2, the fork shafts FS1, FS2, and FS3 have respectivegrooves g1, g2, and g3 which are formed on their circumferentialsurfaces and extend in the axial direction. In addition, pins P1, P2,and P3 are fixed to the fork shafts FS1, FS2, and FS3, respectively,such that they protrude radially outward from their circumferentialsurfaces. The distal ends of the pins P1, P2, and P3 are fitted into thegrooves g3, g1, and g2, respectively. Each of the combination of “thepin P1 and the groove g3,” the combination of “the pin P2 and the grooveg1,” and the combination of “the pin P3 and the groove g2,” constitutesthe above-mentioned “coupling mechanism.”

When both the fork shafts FS1 and FS3 are located in their neutralpositions, the distal end of the pin P1 is located in the center of thegroove g3 in the axial direction (see FIG. 2). In this state, thedistances in the axial direction between the pin P1 and the ends g3 aand g3 b of the groove g3 in the axial direction are each equal to amoving distance in the axial direction of each fork shaft from itsneutral position to the meshing position for the corresponding gearstage (hereinafter, the moving distance will be referred to as the “FSmoving distance C”). Accordingly, when one of the fork shafts FS1 andFS3 is located in the neutral position and the other of the fork shaftsFS1 and FS3 is located in the meshing position for a certain gear stage,the distal end of the pin P1 butts against either one of the ends g3 aand g3 b. In other words, the fork shafts FS1 and FS3 are coupled witheach other in the axial direction.

When both the fork shafts FS1 and FS2 are located in their neutralpositions, the distal end of the pin P2 is located in the center of thegroove g1 in the axial direction (see FIG. 2). In this state, thedistances in the axial direction between the pin P2 and the ends g1 aand g1 b of the groove g1 in the axial direction are each equal to theFS moving distance C. Accordingly, when one of the fork shafts FS1 andFS2 is located in the neutral position and the other of the fork shaftsFS1 and FS2 is located in the meshing position for a certain gear stage,the distal end of the pin P2 butts against either one of the ends g1 aand g1 b. In other words, the fork shafts FS1 and FS2 are coupled witheach other in the axial direction.

When both the fork shafts FS2 and FS3 are located in their neutralpositions, the distal end of the pin P3 is located in the center of thegroove g2 in the axial direction (see FIG. 2). In this state, thedistances in the axial direction between the pin P3 and the ends g2 aand g2 b of the groove g2 in the axial direction ane each egual to theFS moving distance C. Accordingly when one of the fork shafts FS2 andFS3 is located in the neutral position and the other of the fork shaftsFS2 and FS3 is located in the meshing position for a certain gear stage,the distal end of the pin P3 butts against either one of the ends g2 aand g2 b. In other words, the fork shafts FS2 and FS3 are coupled witheach other in the axial direction.

Specifically, as shown in FIG. 4, in a state in which the first gearstage has been realised, the pin P1 butts against the end g3 a, and thepin P2 butts against the end g1 b. In a state in which the second gearstage has been realized, the pin P2 butts against the end g1 b, and thepin P3 butts against the end g2 a. In a state in which the third gearstage has been realized, the pin P3 butts against the end g2 a, and thepin P1 butts against the end g3 b. In a state in which the fourth gearstage has been realized, the pin P1 butts against the end g3 b, and thepin P2 butts against the end g1 a. In a state in which the fifth gearstage has been realized, the pin P2 butts against the end g1 a, and thepin P3 butts against the end g2 b. In a state in which the sixth gearstage has been realized, the pin P3 butts against the end g2 b, and thepin P1 butts against the end g3 a.

When the axial distance between the two heads provided on each forkshaft is denoted by “A” and the width of the inner lever IL in the axialdirection is denoted by “B” as shown in FIG. 5(a), a relation of (A-C)>Bholds as can be understood from FIG. 5(b). Since this relation holds, inthe present apparatus, for the sequential shift (shift from the currentgear stage to an adjacent gear stage), the “operation of cancelling thecurrent gear stage” and the “operation of realizing the adjacent gearstage” can be performed simultaneously. This point will now be describedwith reference to FIGS. 6 and 7.

FIG. 6 shows an operation for the sequential upshift from the secondgear stage to the third gear stage. As shown in FIG. 6(a), in a state inwhich the second gear stage has been realized, the inner lever IL buttsagainst the 2nd head. In this state, since the relation of “(A-C)>B”holds as described above, the inner lever IL can move in the spacebetween the 5th head and the 6th head upon the selection operation. As aresult, as indicated by a thin arrow in FIG. 6(b), by combining theshift operation and the selection operation, it is possible to move theinner lever IL from a “position for butting against the 2nd head” to a“position for butting against the 3rd head” while maintaining the forkshaft FS2 in the meshing position for the second gear stage (namely,without performing an operation of returning the fork shaft FS2 to itsneutral position (an operation of canoeing the second gear stage).

As shown in FIG. 6(c), the shift operation is performed in a state inwhich the inner lever IL butts against the 3rd head. As a result, theinner lever IL presses the 3rd head, so that the fork shaft FS3 movesfrom its neutral position to the meshing position for the third gearstage. At that time, as described above, in the state shown in FIG. 6(b)(namely, the state in which the second gear stage has been realized),the pin P3 butts against the end g2 a (see FIG. 4). Namely, the forkshafts FS2 and FS3 are coupled with each other in the axial direction.Accordingly, simultaneously with the above-described movement of thefork shaft FS3 from its neutral position to the meshing position for thethird gear stage, the fork shaft FS2 moves in the same direction as thefork shaft FS3 from the meshing position for the second gear stage toits neutral position. As described above, the “operation of cancellingthe second gear stage” and the “operation of realizing the third gearstage” can be performed simultaneously.

FIG. 7 shows an operation for the sequential downshift from the secondgear stage to the first gear stage. As in the above-described case ofFIG. 6, as shown in FIG. 7(b), the inner lever IL can move in the spacebetween the 4th head and the 5th head upon the selection operation. As aresult, as indicated by a thin arrow in FIG. 7(b), by combining theshift operation and the selection operation, it is possible to move theinner lever IL from a “position for butting against the 2nd head” to a“position for butting against the 1st head” while maintaining the forkshaft FS2 in the meshing position for the second gear stage (namely,without performing an operation of returning the fork shaft FS2 to itsneutral position (an operation of cancelling the second gear stage).

As shown in FIG. 7(c), the shift operation is performed in a state inwhich the inner lever IL butts against the 1st head. As a result, theinner lever IL presses the 1st head, so that the fort shaft FS1 movesfrom its neutral position to the meshing position for the first gearstage. At that time, as described above, in the state shown in FIG. 7(b)(namely, the state in which the second gear stage has been realized),the pin P2 buts against the end g1 b (see FIG. 4). Namely, the forkshafts FS1 and FS2 are coupled with each other in the axial direction.Accordingly, simultaneously with the above-described movement of thefork shaft FS1 from its neutral position to the meshing position for thefirst gear stage, the fork shaft FS2 moves in the same direction as thefork shaft FS1 from the meshing position for the second gear stage toits neutral position. As described above, the “operation of cancellingthe second gear stage” and the “operation of realizing the first gearstage” can be performed simultaneously.

In the present apparatus, as for all of sequential upshifts andsequential downshifts, in addition to the sequential upshift from thesecond gear stage to the third gear stage and the sequential downshiftfrom the second gear stage to the first gear stage, the “operation ofcancelling the current gear stage” and the “operation of realizing anadjacent gear stage” can be perfonned simultaneously.

Specifically, as can be understood from FIG. 4, in the sequentialupshift from the first gear stage to the second gear stage, the“operation of cancelling the first gear stage” and the “operation ofrealizing the second gear stage” can be performed simultaneously throughutilization of the coupling of the fork shafts FS1 and FS2 realized as aresult of butting between the pin P2 and the end g1 b. In the sequentialdownshift from the third gear stage to the second gear stage, the“operation of cancelling the third gear stage” and the “operation ofrealizing the second gear stage” can be performed simultaneously throughutilization of the coupling of the fork shafts FS2 and FS3 realized as aresult of butting between the pin P3 and the end g2 a.

In the sequential upshift and the sequential downshift between the thirdgear stage and the fourth gear stage, the “operation of cancelling thethird gear stage” and the “operation of realizing the fourth gear stage”can be performed simultaneously and the “operation of cancelling thefourth gear stage” and the “operation of realizing the third gear stage”can be performed simultaneously through utilization of the coupling ofthe fork shafts FS2 and FS3 realized as a result of butting between thepin P1 and the end g3 b.

In the sequential upshift and the sequential downshift between thefourth gear stage and the fifth gear stage, the “operation of cancellingthe fourth gear stage” and the “operation of realising the fifth gearstage” can be performed simultaneously and the “operation of cancellingthe fifth gear stage” and the “operation of realizing the fourth gearstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS1 and FS2 realized as a result of huttingbetween the pin P2 and the end g1 a.

In the sequential upshift and the sequential downshift between the fifthgear stage and the sixth gear stage, the “operation of cancelling thefifth gear stage” and the “operation of realizing the sixth gear stage”can be performed simultaneously and the “operation of cancelling thesixth gear stage” and the “operation of realizing the fifth gear stage”can be performed simultaneously through utilization of the coupling ofthe fork shafts FS2 and FS3 realized as a result of butting between thepin P3 and the end g2 b.

As described above, in the present apparatus, for all of the shiftpatterns; i.e., the sequential upshifts and sequential downshiftsbefeveen gear stages among the first gear stage through the sixth gearstage, the “operation of cancelling the current gear stage” and the“operation of realizing an adjacent gear stage” can be performedsimultaneously. Accordingly, the neutral period becomes shorter ascompared with the conventional apparatus in which the “operation ofrealizing an adjacent gear stage” is performed after the “operation ofcanceling the current gear stage.”

In addition, in the present apparatus, skip shift (gear shift from thecurrent gear stage to a nonadjacent gear stage) can be performed.Specifically, for example, FIG. 8 shows an operation for a skip shiftfrom the third gear stage to the first gear stage. As shown in FIG.8(a), in a state in which the third gear stage has been realized, theinner lever IL butts against the 3rd head. In this state, the shiftoperation is firstly performed as shown in FIG. 8(b). As a result, theinner lever IL presses the 6th head, whereby the fork shaft FS3 moves toits neutral position from the meshing position for the third gear stage.Namely, the neutral state is obtained.

Next, as indicated by a thin arrow in FIG. 8(c), while the neutral stateis maintained, by combining the shift operation and the selectionoperation, the inner lever IL is moved from the “position for buttingagainst the 6th head” to the “position for butting against the 1sthead.”

Subsequently, as a result of performance of the shift operation in thestate in which the inner lever IL butts against the 1st head as shown inFIG. 8(d), the inner lever IL presses the 1st head, whereby the forkshaft FS1 moves from its neutral position to the meshing position forthe first gear stage. As a result the skip shift from the third gearstage to the first gear stage is completed.

As described above, in the present apparatus, after the fork shaftcorresponding to the currently realized gear stage has moved to itsneutral position from the meshing position corresponding to that gearstage, any fork shaft can be moved from its neutral position to ameshing position. Namely, by performing the “operation of realizing thegear stage after the shift operation” after the “operation of cancellingthe gear stage before the shift operation” as in the case of theconventional apparatus, the “skip shift” can be performed as in the caseof the conventional apparatus. In summary, the present apparatus canshorten the neutral period in the sequential shift and can perform theskip shift.

FIG. 9 shows movement patterns of the fork shafts FS1, FS2, and FS3 of atransmission which is a modification of the above-described apparatusand has six gear stages. In the example shown in FIG. 9, the fork shaftFS1 coupled with the “sleeve S1 engageable with the free-rotating gearsG1 o and G2 o” has a 1st head and a 2nd head. The fork shaft FS2 coupledwith the “sleeve S2 engageable with the free-rotating gears G3 o and G4o” has a 3rd head and a 4th head. The fork shaft FS3 coupled with the“sleeve S3 engageable with the free-rotating gears G5 o and G5 o” has a5th head and a 6th head.

In the above-described apparatus, as for all of the shift patterns;i.e., the sequential upshifts and sequential downshifts between gearstages among the first gear stage through the sixth gear stage, the“operation of cancelling the curnant gear stage” and the “operation ofrealizing an adjacent gear stage” can be performed simultaneously. Incontrast, in the example shown in FIG. 9, only as for some of the shiftpatterns (the sequential upshifts and sequential downshifts between gearstages among the first gear stage through the sixth gear stage), the“operation of cancelling the current gear stage” and the “operation ofrealizing an adjacent gear stage” can be performed simultaneously, andas for the remaining shift patterns, the “operation of realizing anadjacent gear stage” can be performed after the “operation of cancellingthe current gear stage” like the conventional apparatus.

Specifically, as for the sequential upshift and the sequential downshiftbetween the first gear stage and the second gear stage, the sequentialupshift and the sequential downshift between the third gear stage andthe fourth gear stage, and the sequential upshift and the sequentialdownshift between the fifth gear stage and the sixth gear stage, the“operation of realizing an adjacent gear stage” is performed after the“operation of cancelling the current gear stage” as in the case of theconventional apparatus.

In the sequential upshift and the sequential downshift between thesecond gear stage and the third gear stage, the “operation of cancellingthe second gear stage” and the “operation of realizing the third gearstage” can be performed simultaneously and the “operation of cancellingthe third gear stage” and the “operation of realizing the second gearstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS1 and FS2 realized as a result of buttingbetween the pin P2 and the end g1 a.

In the sequential upshift and the sequential downshift between thefourth gear stage and the fifth gear stage, the “operation of cancellingthe fourth gear stage” and the “operation of realizing the fifth gearstage” can be performed simultaneously and the “operation of cancellingthe fifth gear stage” and the “operation of realizing the fourth gearstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS2 and FS3 realized as a result of buttingbetween the pin P3 and the end g2 a.

FIGS. 10 and 11 show movement patterns of the fork shafts FS1, FS2, FS3,and FS4 of a transmission having eight gear stages which is obtained byadding fixed gears G7 i and G8 i, free-rotating gears G7 o and G8 o, asleeve S4, and the fort shaft FS4 to the modification shown in FIG. 9.In the example shown in FIGS. 10 and 11, the fork shafts FS1, FS2, andFS3 are the same as those in the example shown in FIG. 9. The fork shaftFS4 coupled with the “sleeve S4 engageable with the free-rotating gearsG7 o and G8 o” has a 7th head and an 8th head.

In FIGS. 10 and 11, the sequential upshifts and the sequentialdownshifts between the first gear stage and the second gear stage,between the second gear stage and the third gear stage, between thethird gear stage and the fourth gear stage, between the fourth gearstage and the fifth gear stage, and between the fifth gear stage and thesixth gear stage are performed in the same manner as in the exampleshown in FIG. 9. In the sequential upshift and the sequential downshiftbetween the sixth gear stage and the seventh gear stage, the “operationof cancelling the sixth gear stage” and the “operation of realizing theseventh gear stage” can be performed simultaneously and the “operationof cancelling the seventh gear stage” and the “operation of realizingthe sixth gear stage” can be performed simultaneously throughutilization of the coupling of the fork shafts FS3 and FS4 realized as aresult, of butting between the pin P4 and the end g3 a. As for thesequential upshift and the seg uential downshift between the seventhgear stage and the eighth gear stage, the “operation of realizing anadjacent gear stage” is performed after the “operation of canceling thecurrent gear stage” as in the case of the conventional apparatus.

FIG. 12 shows movement patterns of the fork shafts FS1, FS2, and FS3 ofa transmission which is a modification of the above-described apparatusand has six gear stages. In the above-described apparatus, threecombinations of “pins and grooves” each constitute the above-mentioned“coupling mechanism.” In contrast, in the example shown in FIG. 12, notonly the combination of “a pin and a groove” but also combinations of“links and grooves” each constitute the above-mentioned “couplingmechanism.”

Specifically, in the example shown in FIG. 12, instead of the pins P2and P3 (see FIG. 2), links L2 and L3 are employed. The link L2 has arod-like shape, and its fulcrum L2 c located in a longitudinal centralportion thereof is connected to the housing (not shown) in a positionbetween the fork shafts FS1 and FS2 such that the link L2 is immovableand rotatable in relation to the housing. Accordingly, the link L2 canrotate about the fulcrum L2 c in relation to the housing.

A first portion L2 a of the link L2 separated from the fulcrum L2 c isconnected to an engagement portion of the fork shaft FS2 such that thefirst portion L2 a is unmovable and rotatable in relation to theengagement portion. A second portion L2 b of the link L2 separated fromthe fulcrum L2 c in a direction opposite the first portion L2 a isfitted into the groove g1. Notably, in actuality, the distances of thefirst and second portions L2 a and L2 b from the fulcrum L2 c changewith the angle of the link L2 in relation to the housing.

When both the fork shafts FS1 and FS2 are located in their neutralpositions, the longitudinal direction of the link L2 is a directionperpendicular to the axial direction of the fork shafts FS1 and FS2(hereinafter simply referred to as the “perpendicular direction”), andthe portion L2 b is located in the center of the groove g1 in the axialdirection (see FIG. 12). When one of the fork shafts FS1 and FS2 islocated in its neutral position and the other of the fork shafts FS1 andFS2 is located in the meshing position for a certain gear stage, thelongitudinal direction of the link L2 inclines from the “perpendiculardirection,” and the portion L2 b butts against either one of the ends g1a and g1 b. In other words, the fork shafts FS1 and FS2 are coupled witheach other in the axial direction.

The link L3 has the same shape as the link L2, and its fulcrum L3 clocated in a longitudinal central portion thereof is connected to thehousing (not shown) in a position between the fork shafts FS2 and FS3such that the link L3 is unmovable and rotatable in relation to thehousing. Accordingly, the link L3 can rotate about the fulcrum L3 c inrelation to the housing.

A first portion L3 a of the link L3 separated from the fulcrum L3 c isconnected to an engagement portion of the fork shaft FS3 such that thefirst portion L3 a is unmovable and rotatable in relation to theengagement portion. A second portion L3 b of the link L3 separated fromthe fulcrum L3 c in a direction opposite the first portion L3 a isfitted into the groove g2. Notably, in actuality, the distances of thefirst and second portions L3 a and L3 b from the fulcrum L3 c changewith the angle of the link L3 in relation to the housing. Each of thecombination of “the pin P1 and the groove g3”, the combination of “thelink L2 and the groove g1,” and the combination of “the link L3 and thegroove g2,” constitutes the above-mentioned “coupling mechanism.”

When both the fork shafts FS2 and FS3 are located in their neutralpositions, the longitudinal direction of the link L3 coincides with the“perpendicular direction”, and the portion L3 b is located in the centerof the groove g2 in the axial direction (see FIG. 12). When one of thefork shafts FS2 and FS3 is located in its neutral position and the otherof the fork shafts FS2 and FS3 is located in the meshing position for acertain gear stage, the longitudinal direction of the link L3 inclinesfrom the “perpendicular direction,” and the portion L3 b butts againsteither one of the ends g2 a and g2 b. In other words, the fork shaftsFS2 and FS3 are coupled with each other in the axial direction.

Specifically, as shown in FIG. 13, in a state in which the first gearstage has been realized, the pin P1 butts against the end g3 a, and theportion L2 b butts against the end g1 b. In a state in which the secondgear stage has been realized, the portion L2 b butts against the end g1b, and the portion L3 b butts against the end g2 b. In a state in whichthe second gear stage has been realized, the portion L2 b butts againstthe end g1 b, and the portion L3 b butts against the end g2 b. In astate in which the third gear stage has been realized, the portion L3 bbutts against the end g2 b, and the pin P1 butts against the end g3 b.In a state in which the fourth gear stage has been realized, the pin P1butts against the end g3 b, and the portion L2 b butts against the endg1 a. In a state in which the fifth gear stage has been realized, theportion L2 b butts against the end g1 a, and the portion L3 b buttsagainst the end g2 a. In a state in which the sixth gear stage has beenrealized, the portion L3 b butts against the end g2 a, and the pin P1butts against the end g3 a.

In the example shown in FIG. 12 as well, the above-described relation of“(A-C)>B” holds. Since this relation holds, as for the sequential shift,the “operation of cancelling the current gear stage” and the “operationof realizing the adjacent gear stage” can be performed simultaneously inthis example as well, as in the case of the above-described presentapparatus. This point will now be described with reference to FIGS. 14and 15.

FIG. 14 shows an operation for the sequential upshift from the secondgear stage to the third gear stage. As shown in FIG. 14(d), in a statein which the second gear stage has been realized, the inner lever ILbutts against the 2nd head. In this state, since the relation of“(A-C)>B” holds as described above, the inner lever IL can move in thespace between the 3rd head and the 5th head upon the selectionoperation. As a result, as indicated by a thin arrow in FIG. 14(b), bycombining the shift operation and the selection operation, it ispossible to move the inner lever IL from a “position for butting againstthe 2nd head” to a “position for butting against the 3rd head” whilemaintaining the fork shaft FS2 in the meshing position for the secondgear stage (namely, without performing an operation of returning thefork shaft FS2 to its neutral position (an operation of cancelling thesecond gear stage)).

As shown in FIG. 14(c), the shift operation is performed in a state inwhich the inner lever IL butts against the 3rd head. As a result, theinner lever IL presses the 3rd head, so that the fork shaft FS3 movesfrom its neutral position to the meshing position for the third gearstage. At that time, as described above, in the state shown in FIG.14(b) (namely, the state in which the second gear stage has beenrealized), the portion L3 b butts against the end g2 b (see FIG. 13).Namely, the fork shafts FS2 and FS3 are coupled with each other in theaxial direction. Accordingly, simultaneously with the above-describedmovement of the fork shaft FS3 from its neutral position to the meshingposition for the third gear stage, the fork shaft FS2 moves, in thedirection opposite the moving direction of the fork shaft FS3, from themeshing position for the second gear stage to its neutral position. Asdescribed above, the “operation of cancelling the second gear stage” andthe “operation of realizing the third gear stage” can be performedsimultaneously.

FIG. 15 shows an operation for the sequential downshift from the secondgear stage to the first gear stage. As in the above-described case ofFIG. 14, as shown in FIG. 15(b), the inner lever IL can move in thespace between the 1st head and the 5th head upon the selectionoperation. As a result, as indicated by a thin arrow in FIG. 15(b), bycombining the shift operation and the selection operation, it ispossible to move the inner lever IL from a “position for butting againstthe 2nd head” to a “position for butting against the 1st head” whilemaintaining the fork shaft FS2 in the meshing position for the secondgear stage (namely, without performing an operation of returning thefork shaft FS2 to its neutral position (an operation of cancelling thesecond gear stage)).

As shown in FIG. 15(c), the shift operation is performed in a state inwhich the inner lever IL butts against the 1st head. As a result, theinner lever IL presses the 1st head, so that the fork shaft FS1 movesfrom its neutral position to the meshing position for the first gearstage. At that time, as described above, in the state shown in FIG.15(b) (namely, the state in which the second gear stage has beenrealized), the portion L2 b butts against the end g1 b (see FIG. 13).Namely, the fork shafts FS1 and FS2 are coupled with each other in theaxial direction. Accordingly, simultaneously with the above-describedmovement of the fork shaft FS1 from its neutral position to the meshingposition for the first gear stage, the fork shaft FS2 moves, in thedirection opposite the moving direction of the fork shaft FS1, from themeshing position for the second gear stage to its neutral position. Asdescribed above, the “operation of cancelling the second gear stage” andthe “operation of realizing the first gear stage” can be performedsimultaneously.

In the example shown in FIG. 12, as in the case of the above-describedpresent apparatus, for all of sequential upshifts and sequentialdownshifts, in addition to the sequential upshift from the second gearstage to the third gear stage and the sequential downshift from thesecond gear stage to the first gear stage, the “operation of cancellingthe current gear stage” and the “operation of realizing an adjacent gearstage” can be performed simultaneously.

Specifically, as is clear from FIG. 13, in the sequential upshift fromthe first gear stage to the second gear stage, the “operation ofcancelling the first gear stage” and the “operation of realizing thesecond gear stage” can be performed simultaneously through utilizationof the coupling of the fork shafts FS1 and FS2 realized as a result ofbutting between the portion L2 b and the end g1 b. In the sequentialdownshift from the third gear stage to the second gear stage, the“operation of canoeing the third gear stage” and the “operation ofrealizing the second gear stage” can be performed simultaneously throughutilization of the coupling of the fork shafts FS2 and FS3 realised as aresult of butting between the portion L3 b and the end g2 b.

In the sequential upshift and the sequential downshift between the thirdgear stage and the fourth gear stage, the “operation of cancelling thethird gear stage” and the “operation of realizing the fourth gear stage”can be performed simultaneously and the “operation of cancelling thefourth gear stage” and the “operation of realizing the third gear stage”can be performed simultaneously through utilization of the coupling ofthe fork shafts FS1 and FS3 realized as a result of butting between thepin P1 and the end g3 b.

In the sequential upshift and the sequential downshift between thefourth gear stage and the fifth gear stage, the “operation of cancellingthe fourth gear stage” and the “operation of realizing the fifth gearstage” can be performed simultaneously and the “operation of cancellingthe fifth gear stage” and the “operation of realizing the fourth gearstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS1 and FS2 realized as a result of buttingbetween the portion L2 b and the end g1 a.

In the sequential upshift and the sequential downshift between the fifthgear stage and the sixth gear stage, the “operation of cancelling thefifth gear stage” and the “operation of realizing the sixth gear stage”can be performed simultaneously and the “operation of cancelling thesixth gear stage” and the “operation of realizing the fifth gear stage”can be performed simultaneously through utilization of the coupling ofthe fork shafts FS2 and FS3 realized as a result of butting between theportion L3 b and the end g2 a.

As described above, in the example shown in FIG. 12 as well, as in thecase of the above-described present apparatus, as for all of the shiftpatterns; i.e., the sequential upshifts and sequential downshiftsbetween gear stages among the first gear stage through the sixth gearstage, the “operation of cancelling the current gear stage” and the“operation of realizing an adjacent gear stage” can be performedsimultaneously. Accordingly the neutral period becomes shorter ascompared with the conventional apparatus in which the “operation ofrealizing an adjacent gear stage” is performed after the “operation ofcancelling the current gear stage.”

In addition, in the example shown in FIG. 12, as in the case of theabove-described present apparatus, skip shift can also be performed.Specifically, for example, FIG. 16 shows an operation for a skip shiftfrom the third gear stage to the first gear stage. As shown in FIG.16(a), in a state in which the third gear stage has been realized, theinner lever IL butts against the 3rd head. In this state, the shiftoperation is firstly performed as shown in FIG. 16(b). As a result, theinner lever IL presses the 6th head, whereby the fork shaft FS3 moves toits neutral position from the meshing position for the third gear stage.Namely, the neutral state is obtained.

Next, as indicated by a thin arrow in FIG. 16(c), while the neutralstate is maintained, by combining the shift operation and the selectionoperation, the inner lever IL is moved from the “position for buttingagainst the 6th head” to the “position for butting against the 1sthead.”

Subsequently, as a result of performance of the shift operation in thestate in which the inner lever IL byte against the 1st head as shown inFIG. 16(d), the inner lever IL presses the 1st head, whereby the forkshaft FS1 moves from its neutral position to the meshing position forthe first gear stage. As a result the skip shift from the third gearstage to the first gear stage is completed.

In summary in the example shown in FIG. 12, as in the case of theabove-described present apparatus, the neutral period in the sequentialshift is short, and the skip shift can be performed.

FIG. 17 shows movement patterns of the fork shafts FS1 and FS2 of atransmission having four gear stages which is obtained by removing thefixed gears G5 i and G5 i, the free-rotating gears G5 o and G6 o, thesleeve S3, and the fork shaft FS3 from the modification shown in FIG.12.

In the example shown in FIG. 17, in the sequential upshift and thesequential downshift between the first gear stage and the second gearstage, the “operation of cancelling the first gear stage” and the“operation of realizing the second gear stage” can be performedsimultaneously and the “operation of cancelling the second gear stage”and the “operation of realizing the first gear stage” can be performedsimultaneously through utilization of the coupling of the fork shaftsFS1 and FS2 realized as a result of butting between the portion L2 b andthe end g1 b.

In the sequential upshift and the sequential downshift between thesecond gear stage and the third gear stage, the “operation of cancellingthe second gear stage” and the “operation of realizing the third gearstage” can be performed simultaneously and the “operation of cancellingthe third gear stage” and the “operation of realizing the second gearstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS1 and FS2 realized as a result of buttingbetween the pin P1 and the end g2 b.

In the sequential upshift and the sequential downshift between the thirdgear stage and the fourth gear stage, the “operation of cancelling thethird gear stage” and the “operation of realizing the fourth gear stage”can be performed simultaneously and the “operation of cancelling thefourth gear stage” and the “operation of realizing the third thirdstage” can be performed simultaneously through utilization of thecoupling of the fork shafts FS1 and FS2 realized as a result of buttingbetween the portion L2 b and the end g1 a.

As described above, in the example shown in FIG. 17 as well, for all ofthe shift patterns; i.e., the sequential upshifts and sequentialdownshifts between gear stages among the first gear stage through thefourth gear stage, the “operation of cancelling the current gear stage”and the “operation of realizing an adjacent gear stage” can be performedsimultaneously.

The present invention is not limited to the above-described embodiment,and various modifications may be employed without departing from thescope of the present invention. For example, in the above-descriedembodiment, etc., a combination of “a pin and a groove” or a combinationof “a link and a groove” is used as the above-mentioned “couplingmechanism.” However, a combination of “a pin and a protrusion” or acombination of “a link and a protrusion” may be used. In this case aswell, the same action and effects are attained.

The combination of “a pin and a protrusion” refers to a structure inwhich in place of a “groove,” protrusions are provided on a fork shaftat positions corresponding to the opposite ends of the groove in theaxial direction, and a distal end portion of the pin is disposed betweenthe two protrusions. The combination of “a link and a protrusion” refersto a structure in which in place of a “groove,” protrusions are providedon a fork shaft at positions corresponding to the opposite ends of thegroove in the axial direction, and the above-mentioned second portion ofthe link is disposed between the two protrusions. In the case where“protrusions” are provided in place of the groove, the coupling betweentwo fork shafts is not realized by butting between the “pin (link)” andthe “ends of the groove in the axial direction” but is realized bybutting between the “pin (link)” and the “protrusions.”

In the above-described embodiment etc., the S&S shaft is disposed so asto be parallel to the fork shafts, the movement of the S&S shaft in theaxial direction corresponds to the shift operation, and the rotation ofthe S&S shaft about its axis corresponds to the selection operation.However, the S&S shaft may be disposed perpendicular to the fork shafts.In this case, the movement of the S&S shaft in the axial directioncorresponds to the selection operation, and the rotation of the S&Sshaft about is axis corresponds to the selection operation.

In the above-described embodiment, etc., the plurality of fork shaftsare driven in the axial direction through use of the S&S shaft. However,the plurality of fork shafts may be driven in the axial directionthrough use of any other drive device without use of the S&S shaft.

In the above-described embodiment, etc., when “skip shift” is performed,it is necessary to perform the “operation of realizing the gear stageafter the shift operation” after the “operation of cancelling the gearstage before the shift operation” as in the case of the conventionalapparatus. However, in above-described embodiment, etc., the combinationof two gear stages for which the “operation of cancelling the gear stagebefore the shift operation” and the “operation of realizing the gearstage after the shift operation” can be performed simultaneously may bechanged from the “combinations of gear stages for sequential shift” tothe “combinations of gear stages for skip shift.” In this case, evenwhen “skip shift” is performed, the “operation of cancelling the gearstage before the shift operation” and the “operation of realizing thegear stage after the shift operation” can be performed simultaneously.

In the above-described embodiment, etc., all the sleeves S1, S2, and S3are provided on the output shaft A3. However, each of the sleeves S1,S2, and S3 may be provided on either one of the input shaft A2 and theoutput shaft A3. Each of the sleeves S1, S2, and S3 is provided on ashaft which is selected from the input shaft A2 and the output shaft A3and on wfiich corresponding free-rotating gears are provided.

1. A power transmission control apparatus for a vehicle comprising: atransmission which includes an input shaft for receiving power from adrive output shaft of a power source of a vehicle and an output shaftfor outputting power to a drive wheel of said vehicle and which has aplurality of gear stages; an actuator for controlling said transmissionso as to selectively realize one gear stage of a plurality of said gearstages; and control means for controlling said actuator based on atravel state of said vehicle, wherein said transmission includes: aplurality of fixed gears each of which is unrotatably provided on saidinput shaft or said output shaft and which correspond to a plurality ofsaid gear stages; a plurality of free-rotating gears each of which isrotatably provided on said input shaft or said output shaft, whichcorrespond to a plurality of said gear stages, and each of which isalways in meshing engagement of said fixed gear for a corresponding gearstage; a plurality of sleeves each of which is provided on acorresponding shaft of said input shaft and said output shaft to beunrotatable and movable in an axial direction in relation to saidcorresponding shaft and each of which is engageable with a correspondingfree-rotating gear of said plurality of free-rotating gears; a pluralityof fork shafts which are provided to be movable in said axial directionand each of which is coupled with a corresponding sleeve of a pluralityof said sleeves to be unmovable in said axial direction in relation tosaid corresponding sleeve, each fork shaft being positioned in a neutralposition in said axial direction so as to establish a state in whichsaid corresponding sleeve is not in engagement with said correspondingfree-rotating gears and being positioned in a meshing position on afirst side and/or a second side of said neutral position in said axialdirection so as to establish a state in which said corresponding sleevecomes into engagement with said corresponding free-rotating gears sothat said corresponding free-rotating gear is unrotatably fixed to saidcorresponding shaft; and a coupling mechanism which is configured to beable to couple first and second fork shafts of a plurality of said forkshafts in said axial direction, each fork shaft being movable betweenits neutral position and said corresponding meshing position(s) whilemaintaining all said remaining fork shafts in their neutral positions,said actuator being configured to drive each of said fork shafts in saidaxial direction, said coupling mechanism being configured such that saidcoupling mechanism does not couple said first and second fork shafts insaid axial direction when both said first and second fork shafts arelocated in their neutral positions, so that, while one of said first andsecond fork shafts is maintained in its neutral position, the other ofsaid first and second fork shafts can be moved, through drive of saidactuator, from its neutral position to said corresponding meshingposition, and when said one fork shaft is located in its neutralposition and the other fork shaft is located in said correspondingmeshing position, said coupling mechanism couples said first and secondfork shafts in said axial direction, so that, when said one fork shaftis moved from its neutral position to said corresponding meshingposition through drive of said actuator, the other fork shaft issimultaneously moved from said corresponding meshing position to itsneutral position.
 2. A power transmission control apparatus for avehicle according to claim 1, wherein said coupling mechanism isconfigured such that when said one fork shaft is located in its neutralposition and the other fork shaft is located in said correspondingmeshing position on said first side, said coupling mechanism couplessaid first and second fork shafts in said axial direction so that, whensaid one fork shaft is moved from its neutral position to saidcorresponding meshing position on said second side through drive of saidactuator, the other fork shaft is simultaneously moved from saidcorresponding meshing position on said first side to its neutralposition.
 3. A power transmission control apparatus for a vehicleaccording to claim 2, wherein said coupling mechanism includes acoupling member which can couple said first and second fork shafts insaid axial direction and is configured such that a first portion of saidcoupling member is coupled with an engagement portion of said first forkshaft to be unmovable and unrotatable in relation to said engagementportion, when both said first and second fork shafts are located intheir neutral positions, a second portion of said coupling memberseparated from said first portion does not butt against an engagementportion of said second fork shaft, and when one of said first and secondfork shafts is located in its neutral position and the other of saidfirst and second fork shafts is located in said corresponding meshingposition, said second portion of said coupling member butts against saidengagement portion of said second fork shaft so that said first andsecond fork shafts are coupled with each other in said axial direction.4. A power transmission control apparatus for a vehicle according toclaim 1, wherein said coupling mechanism is configured such that whensaid one fork shaft is located in its neutral position and the otherfork shaft is located in said corresponding meshing position on saidfirst side, said coupling mechanism couples said first and second forkshafts with each other in said axial direction so that, when said onefork shaft is moved from its neutral position to said correspondingmeshing position on said first side through drive of said actuator, theother fork shaft is simultaneously moved from said corresponding meshingposition on said first side to its neutral position.
 5. A powertransmission control apparatus for a vehicle according to claim 4,wherein said coupling mechanism includes a coupling member which cancouple said first and second fork shafts with each other in said axialdirection, said coupling member is rotatable about a fulcrum of saidcoupling member located between said first and second fork shafts, andsaid coupling member is configured such that a first portion of saidcoupling member separated from said fulcrum is coupled with anengagement portion of said first fork shaft to be unmovable andunrotatable in relation to said engagement portion, when both said firstand second fork shafts are located in their neutral positions, a secondportion of said coupling member separated from said fulcrum in adirection opposite said first portion does not butt against anengagement portion of said second fork shaft, and when one of said firstand second fork shafts is located in its neutral position and the otherof said first and second fork shafts is located in said correspondingmeshing position, said second portion of said coupling member buttsagainst said engagement portion of said second fork shaft so that saidfirst and second fork shafts are coupled with each other in said axialdirection.
 6. A power transmission control apparatus for a vehicleaccording to claim 1, wherein each of said fork shafts has two headswhich are separated from each other in said axial direction and whichcorrespond to two of a plurality of said gear stages, and saidtransmission includes a shift and selection shaft which is provided tobe movable in said axial direction and rotatable about its axis andwhich has an inner lever protruding from a circumferential surface ofsaid shift and selection shaft, wherein, when said shift and selectionshaft is moved in said axial direction or is rotated about said axis,one fork shaft of a plurality of said fork shafts is selected and saidinner lever enters a space between said two heads of said selected forkshaft, and when said shift and selection shaft is rotated about saidaxis or moved in said axial direction, said inner lever presses eitherone of said two heads of said selected fork shaft in said axialdirection so that said selected fork shaft moves in said axial directionfrom its neutral position to said meshing position corresponding to saidpressed head, whereby said gear stage corresponding to said pressed headis realized, said actuator is configured to drive said shift andselection shaft in said axial direction and drive said shift andselection shaft for rotation about said axis, and a distance obtained bysubtracting, from a distance between said two heads provided on eachfork shaft, a moving distance of said fork shaft from said neutralposition to said meshing position, is greater than a width of said innerlever as measured in said axial direction of said fork shaft.